Looking on .bomb at an upcoming SFO-FRA flight I noticed how booking class availability changes, when entering a different "billing address country"

Billing address country "Germany" shows this:

F5, FN5, A5, ON4, O0, J9, JN9, C9, D7, Z2, ZN2, P1, PN0, R0, RN0, IN0, I0, Y9, YN9, B8, M6, E4, U3, H0, HN0, Q0, V0, W0, S0, T0, L0, K0, G0, N0, XN0, X0

Billing address country "United States" shows this:

F5, FN5, A5, ON4, O0, J9, JN9, C9, D9, Z9, ZN9, P6, PN0, R0, RN0, IN0, I0, Y9, YN9, B7, M5, E3, U3, H0, HN0, Q0, V0, W0, S0, T0, L0, K0, G0, N0, XN0, X0

Availability is obviously better for U.S. based billing vs. Germany, e.g. a U.S. based customer might be able to buy some P, Z, class seats, while the German based customer is denied, e.g. pushed into higher and more costly fares.
Not sure how German (and EU-based) customers would like this, if they'd be aware of it.
Something else to look out for. What gives?